Mechanical mice are well known to computer users as a useful tool for positioning a cursor and selecting functions in different applications. These mechanical mice use a ball and related sensors to detect relative motion. However, mechanical mice use relative coordinate tracking, typically have moving parts, are limited to two-dimensional position input, have low resolution, and only work on certain surfaces.
Optical mice use light to detect relative motion. Typically, an optical mouse has a light source, such as a light emitting diode (LED), for illuminating a surface, such as a mouse pad or surface of a table. The light strikes the surface and a portion of the light is reflected. The optical mouse has an on-board detector for detecting the reflected light. Based on the reflected light, an electronic computation unit determines the relative motion of the optical mouse. While optical mice overcome some of the limitations of mechanical mice, they too are limited to two-dimensional position input, use relative coordinate tracking, and do not work on certain surfaces, such as mirrors. Moreover, the LED and electronic computation necessitates the use of a power source in optical mice.